1. Field of the Invention
The present invention generally relates to an anti-thief security sensor assembly and, more particularly, to the anti-thief security sensor assembly of a type wherein while an infrared beam emitted from a beam projecting unit is constantly received by a beam receiving unit, an alarm is generated when an unauthorized intruder traverses across the path of travel of the infrared beam from the beam projecting unit towards the beam receiving unit.
2. Description of the Prior Art
The anti-thief security sensor assembly is known in which a beam projecting unit and a beam receiving unit are installed spaced an appropriate distance from each other with their optical axes aligned with each other as to minimize stray lights, which are reflected from wall surfaces and/or ground surfaces out of the intended path, so that the capability of the sensor assembly to detect passage of an unauthorized intruder can be increased. However, with increase of the distance between the beam projecting unit and the beam receiving unit, alignment of the respective optical axes of the beam projecting unit and the beam receiving unit becomes difficult to achieve, requiring a relatively long time to complete. An exemplary type of the conventional anti-thief security sensor assembly is generally of a design in which when a cover used to protect front regions of the beam projecting unit and receiving unit is removed to detect interference with the detecting operation, light projecting and receiving operations are halted to emit an alarm.
For this reason, during performance of the alignment of the respective optical axes between the beam projecting unit and receiving unit with the cover removed, a timer is manually activated by a servicing person and, during the counting of time performed by the activated timer, the beam projecting and receiving operations are continued even though the cover has been removed, so that the infrared beam can be emitted to facilitate the alignment between the respective optical axes of the beam projecting unit and receiving unit. However, the structure of the conventional anti-thief security sensor assembly in which the infrared beam is emitted only during the counting operation performed by the timer tends force the servicing person to be constantly under pressure that the job of optical alignment must be finished within a predetermined length of time set in the timer and, therefore, it is often experienced that poorly accurate alignment is achieved.
Also, with increase of the distance between the beam projecting unit and the beam receiving unit, alignment of the respective optical axes of the beam projecting unit and the beam receiving unit becomes difficult to achieve, requiring a relatively long time to complete. Specifically, since emission of the infrared beam from the beam projecting unit is halted at the moment the timer counts up, an additional job is required to set the timer on again to allow the beam projecting unit to emit the infrared beam so that the servicing person can continue the alignment job. Accordingly, the alignment job is required to interrupt for a moment, thereby resulting in a loss of contiguity of the alignment job. This in turn brings about reduction in work efficiency and also reduction in alignment accuracy.
In view of the foregoing, the present invention is intended to provide an anti-thief security sensor assembly wherein the alignment of the respective optical axes of the beam projecting unit and receiving unit can be performed continuously over a required length of time.
To this end, the present invention according to one aspect thereof provides an anti-thief security sensor assembly of a type including a beam projecting unit for emitting an infrared beam, and a beam receiving unit for receiving the infrared beam emitted from the beam projecting unit, wherein when a human body or the like intercepts passage of the infrared beam traveling from the beam projecting unit towards the beam receiving unit, the human body or the like can be detected. This anti-thief security sensor assembly also includes a first switch adapted to be activated when a cover protecting the beam projecting unit is removed and for outputting a discriminative signal descriptive of removal of such cover, a transmitting circuit for transmitting the discriminative signal from the beam projecting unit to the beam receiving unit, and a recognizing circuit provided in the beam receiving unit for receiving the discriminative signal and outputting a notifying signal necessary to notify the removal of the cover.
According to the above discussed aspect of the present invention, in the event that the cover protecting the beam projecting unit is removed, the first switch is activated to generate to the beam receiving unit a discriminative signal indicative of the removal of the cover from the beam projecting unit and emission of the infrared beam from the beam projecting unit continues. Accordingly, during performance of a job of aligning respective optical axes of the beam projecting unit and receiving unit with each other with the cover removed, a servicing person can concentrate on the alignment job without worrying about the length of time permitted to perform it and, hence, not only can the work efficiency of the alignment job be increased, but also the accuracy of the optical alignment can be increased.
Also, since the recognizing circuit provided in the beam receiving unit is operable in response to receipt of the discriminative signal to output the notifying signal indicative of the removal of the cover for the beam projecting unit and, therefore, the beam receiving unit can recognize the removal of the cover from the beam projecting unit to thereby trigger the alarm.
The present invention in accordance with another aspect thereof provides an anti-thief security sensor assembly of a type including a beam projecting unit for emitting an infrared beam, and a beam receiving unit for receiving the infrared beam emitted from the beam projecting unit, wherein when a human body or the like intercepts passage of the infrared beam traveling from the beam projecting unit towards the beam receiving unit, the human body or the like can be detected. This anti-thief security sensor assembly also includes a second switch adapted to be manually operated to output to the beam projecting unit a discriminative signal indicative of a job of aligning respective optical axes of the beam projecting unit and receiving unit with each other being performed, a transmitting circuit for transmitting the discriminative signal from the beam projecting unit to the beam receiving unit, and a recognizing circuit provided in the beam receiving unit for receiving the discriminative signal and outputting a notifying signal to notify the removal of the cover.
According to the second mentioned aspect of the present invention, when a servicing person removes the cover from the beam projecting unit preparatory to the optical alignment being performed and subsequently manipulates the second switch, a discriminative signal indicative of the removal of the cover from the beam projecting unit is outputted to the beam receiving unit and emission of the infrared beam from the beam projecting unit continues. Accordingly, during performance of a job of aligning respective optical axes of the beam projecting unit and receiving unit with each other with the cover removed, a servicing person can concentrate on the alignment job without worrying about the length of time permitted to perform it and, hence, not only can the work efficiency of the alignment job be increased, but also the accuracy of the optical alignment can be increased.
In one preferred embodiment of the present invention, the transmitting circuit referred to above may be operable to superimpose the discriminative signal on the infrared beam emitted from the beam projecting unit and, in such case, the recognizing circuit is operable to discriminate the discriminative signal from the infrared beam received by the beam receiving unit.
According to this preferred embodiment, the discriminative signal is supplied to the beam receiving unit having been superimposed on the infrared beam emitted from the beam projecting unit and the recognizing circuit in the beam receiving unit discriminates the discriminative signal. Accordingly, the anti-thief security sensor assembly of the present invention doe not require an extra use of a device solely for transmitting and receiving the discriminative signal and can therefore be simplified in structure.